Help, what is this?

[Elysee]

Dear all,

my mother had her second chemo this monday. The mastectomy was in the beginning of october. She had a 2,5 cm in der left breast, G3, Ki67:60% and one involved node (the sentinel). She is er-pr-her2++++. So today she found a lump in the crook of her arm. It is sunday in germany and I cant reach anybody. Could this be a metastasis? I know the crook of the arm is an unusual place for metastasis but I found out that there are lymphnodes there too. I am so scared. She said the lump does not hurt.
Any advice could be helpful

Thanks
Elise